java - MAT space vs. TaskManager space -

java - MAT space vs. TaskManager space -

after searching web while decided inquire help problem.

my programme should analyze logfiles, big. 100mb 2gb. want read files using nio-classes filechannel.

i don't want save files in memory, want process lines immediately. code works.

now problem: analyzed memory usage eclipse mat plugin , says 18mb of info saved (that fits). taskmanager in windows says 180mb used jvm.

can tell me why is?

i don't want save info reading filechannel, want process it. closing channel afterwards - thought every info deleted then?

i hope guys can help me difference between used space shown in mat , used space shown in taskmanager.

mat show objects actively references program. jvm uses more memory that:

its own code non-object info (classes, compiled bytecode e.t.c.) heap space not in use, has been allocated.

the lastly case major one. depending on how much physical memory there on computer, jvm set default maximum size heap. improve performance maintain using amount of memory minimal garbage collection activity. means objects no longer referenced remain in memory, rather garbage collected immediately, increasing total amount of memory used.

as result, jvm not free memory has allocated part of heap system. show-up inordinate amount of used memory in os monitoring utilities.

applications high object allocation/de-allocation rates worse - have application uses 1.8gb of memory, while requiring less 100mb. reducing maximum heap size 120 mb, though, increases execution time total order of magnitude.

java heap mat